Photographic camera



April 16, y.1940. H. sAuER Er Ax. 2,197,194

PHOTOGRAPHIC CAMERA Original Filed Feb 2, 1938 2 Sheets-Sheet 1 April 16, 1940. H. sAUER Er AL 2,197,194

PHOTOGRAPHIC CAMERA Original Filed Feb. 2, 1958 2 Sheets-Sheet 2 Hmz: fa/zar Para! 60?/[6/5 Patented Apr. 16, 1940 PATENT OFFICE A PHOTOGRAPHIC CAMERA Hans Sauer and Paul Grllch, Dresden, Germany, assignors to Zeiss Ikon Aktiengesellschaft,

Dresden, Germany Original application February 2, 1938, Serial No.

188,374. Divided and this application September 22, 1939, Serial No. 296,020. In Germany January 13, 1937 7 Claims.

'I'his invention is a division of our application for Letters Patent led in the United States Patent Ofllce on the 2nd day of February 1938, Serial No. 188,374 relating to improvements in exposure 5 meters, and particularly to improvements in exposure meters permanently combined with photographic cameras.

It is an object of the invention to increase the sensitiveness of the meter by utilization of a reyeczting galvanometer as a part of the exposure me er.

It is furthermore an object of the invention to` facilitate the reading of the indicating beam by lengthening the path of the indicating beam between the movable mirror of the galvanometer and the translucent screen on which the position of the indicator beam can be observed.

`It is furthermore an object of the invention to reduce the volume of the instrument by de- 90 liecting the path'of light between the point of entry in the instrument and the movable mirror of the galvanometer, whereby the galvanometer mirror may be positioned out of line with the inlet opening for the light, and whereby an optical element for focusing the light may be inserted between the inlet opening and the mirror ofthe galvanometer.

It is furthermore an object of the invention to render beam deilecting means adjustable in order to cause the beam to appear on a predetermined point of a translucent screen on which it is to be observed, and to combine the adjustable deilecting means with means for controlling the exposure.

It may, therefore, also be described as an object of the invention to combine a beam regulating means with an exposure control means of the camera, whereby upon the appearance of the beam at a predetermined point of the translucent 0 screen, indication is furnished that the control means for the exposure has been adjusted to the desired position.

With these and numerous other objectsl in view, an embodiment of the invention has been de- 5 scribed by way of example in the following specification and shown in the accompanying drawings to which reference is made in the speciiication.

In the drawings:

Fig.` 1 is partly a top, plan view andpartly a horizontal section through a camera combined with an exposure meter and mirror galva-v nometer;

Fig. 2 is a front elevation of the camera and exposure meter, certain parts being shown in section;

Fig. 3 is a top plan viewpof a detail ofthe adjusting means;

Fig. 4 is a rear elevation of the camera with 5 the observation window for the indicator beam, and

Fig. 5 is a simplied diagrammatical representation of the exposure meter and the optical equipment. l 10 In the embodiment illustrated by way of example, the exposure meter is shown as being combined with the housing i of a camera. The latter has a mounting 2 preferably detachable, for a suitable lens 3, and is also provided with exposure control means, as for instance, a diaphragm ring 4 through which the effective aperture of the lens 3 may be varied as demanded by the light conditions and other conditions for the exposure. The diaphragm itself is shown in the drawings at'3E.

The means for focal adjustment of the lens 3 may be constructed in any desired way and do not form any part of the present invention. Similarly also, the construction of the diaphragm may be selected as desired, and no claim is made to the specific construction of these parts.

The exposure meter illustrated by way of example also is of the known current generating type in which the light striking a photosensitive cell energizes said cell to produce an electric current, the intensity of which depends upon the strength of illumination. The intensity of this current may be determined by a galvanometer within the circuit. Devices of this typeare now generally known and are frequently employed either in xed association with the camera itself or detached from the camera.

In the embodiment illustrated, the front wall of the camera has an opening in which the photosensitive cell 5 is located. The electric current generated upon illumination of the cell is carried through conductors, not shown, to the movable system of a galvanometer 6, the stationary part .of which is formed by the magnet 1. A variable resistance 8, Fig. 2, may be interposed between the source of current 5 and the measuring instrument 6, and as in similar devices of this character, the variation of the resistance is effected by supporting the same movably relatively to a stationary contact member 9 in the circuit.

While in photographic exposure meters the movable system 6 of the galvanometer generally causes a pointer to move relatively to a scale, in the present Ainvention the sensitiveness oi the instrum ent is greatly enhanced by converting this galvanometer into a mirror galvanometer, yand by providing a longer path for the beam of light refiected by the mirror than it normally would be in an instrument as compact and compendious as instruments of this character necessarily have to be.

For this purpose the indicating beam of light reflected from the mirror of the galvanometer is reflected, preferably a plurality of times, between the mirror I0 and the translucent observation window, so that this path is considerably longer than the actual distance between the mirror Ill and the translucent screen.

The front wall of the housing I is provided with a small or narrow slit I I shown near the bottom and through which the light enters to strike a reector I2 preferably in a fixed position in the interior of the housing. The light reilected by the mirror I2 is thrown upon another mirror or reflector I3 to be reflected thereby upon the galvanometer mirror I0.

For the purpose of producing a very sharp picture of the beam of light entering the slit Il in the housing, means for condensing said beam may be provided between the point of entry and the movable reflector I0 of the galvanometer. By way of example a compound lens I4 adapted to produce a very sharp picture of the beam of light is shown interposed between the reflectors I2 and I3 in the embodiment illustrated. Owing to this multiple deflection, the location of the mirror I0 also need not be in alinement with the slit I I, so as to make the instrument very compact and narrow, without sacricing the sensitiveness due to the mirror galvanometer.

The beam of light reflected by the mirror I 0 is not projected directly upon the translucent screen, but its path also is lengthened to produce a broad sweep over said screen. In the embodi- I ment shown, the beam reflected from mirror III is directed toward the reflector I3 although it is obvious that in place of this reflector which had been used for the incident beam of light, another reiiector might be positioned in the path of the reflected beam. The light is then reflected from mirror I3 to a reector I5, from which last named reiiecting means it is projected upon the translucent screen I6. This screen is preferably disposed in the rear wall of the camera, and as shown in Fig. 4, a plurality of markings I1 are provided thereon permitting the observer to read the posi- 'tion of the indicator beam I8 with respect to any of these indications.

One of the deilecting means is coupled with one of the elements for controlling the exposure condition. 1`

' In the embodiment illustrated, the reector I5 is mounted on a shaft 20, which is rotatable in the housing. The upper end of shaft enters the bearing stud I9, which may be fixed in the housing. Abevel gear 2 I on shaft 2II is in operative relation to the bevel gear 22, with which a train of spur gears 23. 24 and 25 is associated, the last named gear being iixedly connected with another gear 26 in mesh with the gear rim 28 on the ringV 29, and this last named ring is connected with the diaphragm 4 of the camera.

The adjustment of the resistance 8 is e'ected by turning a knob 30 which is accessible from the outside of the housing and which has a bevelled base 3i adapted to be set selectively with respect to a flxed mark 32 also disposed on the housing. The bevelled disc 8i preferably carries indications of the shutter speed, and by rotation of the knob 30, therefore, the shutter may be set to the speed indicated for which purpose a mechanism, not illustrated herein, but well known by itself, may be used.

In the use of the device, the operator advisably selects through rotation of the knob the exposure time which may depend upon the nature of the object, whether movable or stationary, and which also may be selected under consideration of the light conditions as estimated by the operator. Rotation of the knob 30 not only adjusts the shutter to the desired speed, but also determines the value of the resistance 8 within the circuit of the galvanometer and photoelectric cell. If then the photoelectric cell 5 is exposed to the light reflected by the object, the current set up in the circuit of this cell will bring about a deection of the movable system of the galvanometer, depending on the one hand upon the light condition, and on the other hand upon the resistance 8. The current imparts movement to the mirror I0, so that the beam I8 travels over the screen I6 at the rear face of the camera. This rear face is directed towards the operator, and hence the location of the beam is continuously under observation of the user.` The translucent screen I6 has markings I'l' which may indicate the stop to be used at the selected shutter speed. It is also feasible, however, to turn now the ring 34 which is connected with the diaphragm ring 4 and has a diaphragm aperture scale 35 thereon, in order to actuate the train of gears 28 to 2| inclusive, whereby a rotary movement of the adjustable reflector I5 is set up, thereby influencing the position of the beam on the face of the transparent screen.

This adjustment, preferably, is continued until the beam I8 reaches a predetermined position, as for instance, a zero or central position upon the screen. When this condition has been attained, the operator has selected the proper diaphragm for the speed which previously had been selected.

The invention, however, is not intended to be limited to the embodiment described and shown. It is possible for instance to effect positive setting of the second adjustable exposure control element, namely the diaphragm or stop, when the first exposure control element, namely the shutter, is set to a certainspeed value. This could be accomplished by returning the indicator beam to a predetermined position, as for instance zero position, by turning a reflector. It could also be accomplishedby havingv a second beam, or other indicator means, in lagging or leading cooperation with the indicator beam.

f We claim: g

l. In a photographic camera. united with a photoelectric'exposure meter. the combination of a camera casing having a front wall and a rear wall, a photoelectric cell ,mounted on said front wall, a translucent screen in said rear wall, a mirror galvanometer within said camera casing and adapted to be operated by the current released by the photoelectric cell, means for projecting a beam of light upon the movable mirror of the galvanometer, adjustable light defiecting means interposed between said movable mirror and said translucent screen, manually operable means for controlling the exposure yoi! a film placed in the camera, and means for operatively coupling said adjustable deiiecting means with 2. In a photographic camera the combination with a photoelectric exposure meter, of a camera casing having a front wall and a rear wall, a photoelectric cell on said front wall, a mirror galvanometer within said camera casing, a variable resistance in the circuit of said exposure meter, the front wall of said camera casing having a slit-shaped opening through which light may pass to the movable mirrior of said galvanometer, two exposure controlling elements forming parts of the camera, a translucent screen in the rear wall of said camera casing, means for deflecting the light reflected from said movable mirror upon said translucent screen, said deflecting means being adjustable and being coupled with one of said two exposure controlling elements of the camera, whereby upon actuating said exposure controlling element the deilecting means lis adjusted at the same time, and means operatively connecting the other exposure controlling element ofthe camera with said variable resistance for adjusting the beam of light to a predetermined point of said translucent screen after said first named exposure controlling element has been adjusted. *A

3. A photographic camera comprising in combination with a photoelectric exposure meter, a camera casing having a front wall and a rear wall, a photoelectric cell on said front wall, a mirror galvanometer within said camera casing and adapted to be actuated by the current released by the photoelectric cell, the front wall of the camera casing having a slit-shaped opening through which light may pass to the movable mirror of the galv'anometer, a translucent screen in the rear wall of the camera casing, adjustable means for deflectlng the beam of light reflected by said movable mirror upon said translucent screen, a photographic objective having a manually adjustable diaphragm on said front wall of the camera casing, means for operatively connecting said adjustable diaphragm with said adjustable means which dellects the beam of light reflected by said movable mirror of the galvanometer, a shutter speed setting member, means for varying the current in the circuit of said exposure meter, and means operatively connecting said shutter speed setting member with said current varying means, whereby after a previous adjustment of the diaphragm the beam of light by' actuating the shutter speed setting member may be adjusted to appear at a predetermined point of said translucent screen, which indicates a correct adjustment of the diaphragm and shutter for the prevailing light condition.

4. In a photographic camera, the combination of a photoelectric exposure meter, a camera casing having atop. wall, a front wall and a rear wall, a photographic objective on said front wall, said photoelectric exposure meter including within a circuit a photoelectric cell mounted on said front wall, a variable resistance and a mirror galvanometer within said camera casing, the front wall of said camera casing being provided with a slit, a translucent screen in said rear wall of said camera casing, two reflecting members within said camera casing for reflecting the beam of light entering said camera casing through said slit onto the movable mirror of said mirror galvanometer, one of said reflecting members being positioned to reflect the beam of light a second time after said beam of light has been reflected by said movable mirror, a third reflecting member within said camera casing for receiving the beam of light reflected from said movable mirror onto said last named reflecting member to reflect this beam onto said translucent screen, a manually operable shutter speed adjusting member on said top wall and operatively connected with said variable resistance for varying the same whenever said shutter speed adjusting member is operated.

5. In a photographic camera, the combination of a photoelectric exposure meter, a camera casing having a top wall, a front wall and a rear wall, a photographic objective on said front wall and provided with an adjustable diaphragm and a manually rotatable diaphragm adjusting ring, said photoelectric exposure meter including within a circuit a photoelectric cell mounted on said p front wall, a variable resistance and a mirror galvanometer within said camera casing, the front wall of said camera casing being provided with a slit, a translucent screen in said rear wall of said camera casing, two reflecting members within said camera casing for reflecting the beam of light entering said camera casing through said slit onto the movable mirror of said mirror galvanometer, one of said reilecting members being positioned to reflect the beam of light a second time after said beam of light has been reflected by said movable mirror, a third reflecting member within said camera casing for receiving the beam of light reflected from said movable mirror onto said last named reflecting member to reiiect this beam onto said translucent screen, and a manually operable shutter speed adjusting member on said top wall and operatively connected with said variable resistance for varying the same whenever said shutter speed adjusting member is operated, and means operatively connecting said diaphragm adjusting ring with said third reflecting member for adjusting the latter whenever the diaphragm adjusting ring is operated.

6. In a photographic camera, the combination of a photoelectric exposure meter, a camera casing having a front wall and a rear wall, a photographic objective with a variable diaphragm on said front wall, said exposure meter including within a circuit a photoeectric cell mounted ion said front wall adjacent said objective, a variable resistance and a mirror galvanometer within said camera casing, the front wall of said camera casing being provided with a slit, a translucent screen in said rear wall of said camera casing, two reflecting members within said camera casing for reflecting the beam of light entering said camera casing through said slit onto the movable mirror of said mirror galvanometer, one of said reflecting members being positioned to reflect the beam of light a second time after said beam of light has been reflected by said movable mirror, a third reflecting member within said camera casing for receiving the beam of light reflected from said movable mirror onto said last named reflecting member to reflect this beam onto said translucent screen, and a manually operable shutter speed adjusting member operatively connected with said variable resistance for varying the latter whenever said shutter speed adjusting member is operated, said translucent screen being provided With a diaphragm aperture scale.

'1. In a photographic camera, the combination of a photoelectric exposure meter, a camera casing having a front wall and a rear wall, a photographic objective with a variable /diaphrag'm on said front Wall, said exposure meterincluding within a circuit a photoelectric cell mounted on said front wall adjacent said objective, a vari- 75 able resistance and a mirror galvanometer within said camera casing, the front wall of said camera casing being provided with a slit, a translucent screen in said rear wall of said camera casing, two reilecting members within said camera casing for reflecting the beam of light entering said camera casing through said slit onto the movable mirror of said mirror galvanometer, one of said reflecting members being positioned to reiiect the beam of light a second time after said beam of light has been reiiected by said movable mirror, a third reflecting member Within said camera casing for receiving the beam of light reiiected from said movable mirror onto said last named reiiecting member to reiiect this beam onto said translucent screen, a manually operable shutter speed adjusting member operatively connected with said variable resistance for varying the latter whenever said shutter speed adjusting memberis operated, and means operatively connecting the variable diaphragm or said photographic objective with said third reiiecting member for adjusting the latter whenever the diaphragm is 10 adjusted to another aperture.

HANS BAUER. PAUL Gmcrr. 

